java如何通过连接持久化实体?
我对如何使用列的联接在db中保存条目感到困惑。我有@实体吼叫
@XmlRootElement
@XmlAccessorType(value = XmlAccessType.FIELD)
@Entity
@Table(name = "psc_users")
@NamedQuery(name = "User.findAll", query = "SELECT u FROM User u")
public class User implements Serializable {
private static final long serialVersionUID = 8885916014620036457L;
@Id
private static final String SEQUENCE_NAME = "psc_users_user_id_seq";
@Id
@GeneratedValue(generator = "UseExistingOrGenerateIdGenerator",
strategy = GenerationType.SEQUENCE)
@GenericGenerator(name = "UseExistingOrGenerateIdGenerator",
strategy = "com.psc.util.UseExistingOrGenerateIdGenerator",
parameters = {
@org.hibernate.annotations.Parameter(name = "sequence", value = SEQUENCE_NAME)
}
)
@Column(name = "USER_ID")
private Long userId;
@Column(name = "DEF", length = 30)
private String def;
@Temporal(TemporalType.TIMESTAMP)
@Column(name = "DEL_DATE")
private Date delDate;
@Column(name = "DISPLAY_DEF", length = 60)
private String displayDef;
@Column(name = "EMAIL", length = 60)
private String email;
@Temporal(TemporalType.TIMESTAMP)
@Column(name = "NAVI_DATE")
private Date naviDate;
@Column(name = "NAVI_USER")
private String naviUser;
@Column(name = "PHONE", length = 30)
private String phone;
@Column(name = "PWD", length = 40)
private String pwd;
//bi-directional many-to-one association to Branch
@ManyToOne(cascade = CascadeType.MERGE)
@JoinColumn(name = "BRNC_BRNC_ID", nullable = false)
private Branch pscBranch;
public Long getBrncBrncId() {
return brncBrncId;
}
public void setBrncBrncId(Long brncBrncId) {
this.brncBrncId = brncBrncId;
}
@Column(name = "BRNC_BRNC_ID", insertable = false, updatable = false)
private Long brncBrncId;
//bi-directional many-to-one association to User
@ManyToOne(cascade = CascadeType.MERGE)
@JoinColumn(name = "CURATOR_USER_ID")
private User pscUser;
public Long getCuratorUserId() {
return curatorUserId;
}
public void setCuratorUserId(Long curatorUserId) {
this.curatorUserId = curatorUserId;
}
@Column(name = "CURATOR_USER_ID", insertable = false, updatable = false)
private Long curatorUserId;
public User() {
}
public Long getUserId() {
return this.userId;
}
public void setUserId(Long userId) {
this.userId = userId;
}
public String getDef() {
return this.def;
}
public void setDef(String def) {
this.def = def;
}
public Date getDelDate() {
return this.delDate;
}
public void setDelDate(Date delDate) {
this.delDate = delDate;
}
public String getDisplayDef() {
return this.displayDef;
}
public void setDisplayDef(String displayDef) {
this.displayDef = displayDef;
}
public String getEmail() {
return this.email;
}
public void setEmail(String email) {
this.email = email;
}
public Date getNaviDate() {
return this.naviDate;
}
public void setNaviDate(Date naviDate) {
this.naviDate = naviDate;
}
public String getNaviUser() {
return this.naviUser;
}
public void setNaviUser(String naviUser) {
this.naviUser = naviUser;
}
public String getPhone() {
return this.phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public String getPwd() {
return this.pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
public Branch getPscBranch() {
return this.pscBranch;
}
public void setPscBranch(Branch pscBranch) {
this.pscBranch = pscBranch;
}
public User getPscUser() {
return this.pscUser;
}
public void setPscUser(User pscUser) {
this.pscUser = pscUser;
}
}
如果我保存用户实例时没有字段pscUser(此处为null),但存在具有正确值的有效CuratorUserId,那么我最终会遇到数据库中CuratorUserId为空的情况。如果您查看代码,就会看到这些绑定字段
@ManyToOne(cascade = CascadeType.MERGE)
@JoinColumn(name = "CURATOR_USER_ID")
private User pscUser;
@Column(name = "CURATOR_USER_ID", insertable = false, updatable = false)
private Long curatorUserId;
保存用户的代码
repositoryUser.save(user);
这是我在调试器中看到的
这是我在保存用户后在数据库中看到的
很抱歉我提出了一个愚蠢的问题,但我遇到了一个不同的行为,我的项目中有一个以另一种方式运行的代码。我不想搜索实际的另一个用户(策展人)来保存我的用户,因为查询的开销很大
# 1 楼答案
您的映射应如下所示:
你需要从对象的角度来思考。只有将pscUser引用设置为用户实例时,才会在数据库中设置FK。如果这是现有用户,则需要设置对现有持久实体的引用
# 2 楼答案
真正的答案是,我有两点可以保存和更新我的实体。请看这个Hibernate: Where do insertable = false, updatable = false belong in composite primary key constellations involving foreign keys?
# 3 楼答案
curetorUserId字段上的@Column注释具有属性 insertable=false和Updateable=false,这意味着在插入和更新期间忽略其值
您可以将这些属性更改为true(但它可能会在其他地方破坏您的应用程序),也可以使用EntityManager填写pscUser字段。getReference,它只是创建一个代理,实际上并不生成对数据库的查询